In a typical ink-jet recording or printing system, ink droplets are ejected from a nozzle at high speed towards a recording film, element, or medium to produce an image on the film. The ink droplets, or recording liquid, generally comprise a recording agent, such as a dye or pigment, and a large amount of solvent. The solvent, or carrier liquid, typically is made up of water, an organic material such as a monohydric alcohol, a polyhydric alcohol or mixtures thereof.
An ink-jet recording film typically comprises a support having on at least one surface thereof an ink-receiving or image-forming layer, and includes those intended for reflection viewing, which have an opaque support, and those intended for viewing by transmitted light, which have a transparent support.
In order to achieve and maintain photographic-quality images on such an image-recording film, an ink-jet recording film must:
Be readily wetted so there is no puddling, i.e., coalescence of adjacent ink dots, which leads to non-uniform density.
Exhibit no image bleeding.
Exhibit the ability to absorb high concentrations of ink and dry quickly to avoid films blocking together when stacked against subsequent prints or other surfaces.
Exhibit no discontinuities or defects due to interactions between the support and/or layer(s), such as cracking, repellencies, comb lines and the like.
Not allow unabsorbed dyes to aggregate at the free surface causing dye crystallization, which results in bloom or bronzing effects in the imaged areas.
Have an optimized image fastness to avoid fade from contact with water or radiation by daylight, tungsten light, or fluorescent light.
In addition, a transparent ink-jet recording film suitable for medical imaging output must provide:
A transparent maximum optical density of at least about 2.8.
A grey scale sufficient to distinguish among the densities of various body structures.
A haze value at least that of current medical X-ray films (i.e., about 26 or less).
An ink-jet recording film that simultaneously provides an almost instantaneous ink dry time and good image quality is desirable. However, given the wide range of ink compositions and ink volumes that an ink-jet recording film needs to accommodate, these requirements are difficult to achieve simultaneously.
Ink jet recording films are known that employ porous or non-porous single layer or multilayer coatings that act as suitable image-receiving layers on one or both sides of a porous or non-porous support. Recording films that use non-porous coatings typically have good image quality but exhibit poor ink dry time. Recording films that use porous coatings typically contain colloidal particulates and have poorer image quality but exhibit superior dry times.
While a wide variety of porous image-recording films for use with ink-jet printing are known, there are many unsolved problems in the art and many deficiencies in known products which have severely limited their commercial usefulness.
A challenge in the design of a transparent porous ink-receiving layer for ink jet films is providing high quality, crack-free coatings with as little non-particulate matter as possible. If too much non-particulate matter is present, the image-recording layer will not be porous and will exhibit poor ink dry times. If too much particulate matter is present, the image recording layer will have a high level of haze or will exhibit cracking.
An additional challenge in preparing transparent ink-jet recording films is providing images having high density. Typical ink-jet films use a reflective backing. In these films, a high density image is achieved because light is absorbed as it passes into the imaged film and again, upon reflection, as it passes out of the film. For transparent films, such as those used to record medical X-rays, the high density image must be achieved by laying down a large amount of ink. However, the large amount of ink required leads to slow drying images. To compensate for the slow drying, heaters and/or slow through-put are required.
U.S. Pat. No. 4,877,686 (Riou et al.) describes a recording sheet for ink jet printing wherein boric acid or its derivative is used to cause gelling in a polymeric binder containing hydroxyl groups and a filler comprising particles. However, there is a problem with this recording sheet in that the amount of boric acid used does not provide a recording sheet which, when printed with an ink-jet printer, will have a fast dry time without cracking.
U.S. Patent Application Publication 2004/0022968 (Liu et al.) describes an ink jet recording element comprising a subbing layer comprising a polymeric binder and a borate and an image-receiving layer comprising a cross-linkable polymer and inorganic particles. Surfactants are present in the image-receiving layer at up to about 0.5 wt %.
U.S. Pat. No. 6,908,191 (Liu et al.) describes an ink jet printing method. A coating aid may be present in the image-receiving layer of from 0.01 to 0.30 wt % based on the total solution weight.
U.S. Pat. No. 6,623,819 (Missell et al.) describes an ink jet recording element. A coating aid may be present in the image-receiving layer of from 0.01 to 0.30 wt % based on the total solution weight.